A laser ignition device is described, for example, in PCT Application No. WO 2005/0066488 A1.
An ignition laser has a combustion chamber window that is transparent to the laser pulses emitted from the ignition laser. An aperture stop is described in PCT Application No. WO 2010/057904 in order to protect the combustion chamber window from contaminants or damage during operation of the internal combustion engine. The combustion chamber window is not protected, however, during the time period between functional testing during manufacture and initial startup of the internal combustion engine, or during extended stoppage phases prior to startup of the internal combustion engine. In the context of installation of the new part, the combustion chamber window can become soiled as a result of an unclean working environment in the shop, contaminants in the spark plug hole, condensation during the cold engine starting operation, or sprayed oil from the internal combustion engine. After extended stoppage phases, particle accumulation or condensation in particular can negatively affect the service life of the combustion chamber window or even result in malfunction of the laser ignition device.